Lumbar support device

ABSTRACT

A lumbar support device for a vehicle seat is comprised a seat back frame comprising the side frames and an upper frame connecting an upper portion of each side frame, a spring member, and a support body supporting a part of the spring member so as to be movable in front and back directions relative to the seat back by a drive device. The lumbar support device also includes a retracting restriction mechanism disposed between the support body and the drive device or between the support body and the spring member to prevent the spring member from moving backward relative to the seat back when a load applied to the spring member is equal to or more than a predetermined value.

CROSS REFERENCE OF RELATED APPLICATION

[0001] This application is based on and claims priority under 35 U.S.C. §119 with respect to Japanese Application No. 2001-323991 filed on Oct. 22, 2001, the entire content of which is incorporated herein by reference.

FIELD OF THE INVENTION

[0002] This invention relates to a lumbar support device which is mounted in a seat for a vehicle, and more particularly, the present invention relates to a lumbar support device which can variably change the shape of the vehicle seat.

BACKGROUND OF THE INVENTION

[0003] A known device is disclosed in Japanese Patent Laid-Open Publication No.2001-145539. The known device is provided with an inverted U-shaped seat back frame, and a flat spring member is provided in a space within the inverted U-shape of the seat back frame. In order to support a passenger's lumbar accurately, a lumbar support device is disposed in a seat at a position of a seat corresponding to a passenger's lumber to move a part of the flat spring member so that the seat position corresponding to the passenger's lumber is adjustable in forward and backward direction relative to the seat. The lumbar support device is comprised of a double crank rod rotatably supported by a vertical member relative to the seat back frame and an elastic connecting member interposed between an eccentric axis of the crank rod and a support plate.

[0004] However, with the above mechanism which interposes the elastic connecting member between the eccentric axis of the crank rod and a support plate, when a load greater than a normal use is applied to the seat back from the passenger side, a seating surface is pushed backward. Other than a normal use of a lumbar support device which adjusts a shape of a seat back in accordance with a posture during driving, there is a demand from passengers for the lumbar support device that can reduce fatigue by raising a part of the seat back corresponding to the passenger's lumbar so that the passenger can stretch a body after a long drive. In this case, the seat back receives a greater weight of a passenger than a weight in a normal seating posture. However, with the known lumbar support which raises the seat back with a known spring force, the lumbar support is pushed backward because the spring force cannot support the greater load than the normal use. Thus, the known device is insufficient in providing an effective stretch support to the passenger.

SUMMARY OF THE INVENTION

[0005] It is an object of the present invention to provide an improved lumbar support device which can obviate the above drawbacks.

[0006] According to the present invention, a lumber support device is comprised of a seat back frame having a pair of side frames located right and left sides relative to a seat back and extending in a vertical direction relative to the seat back and an upper frame connecting an upper portion of each side frame, a spring member is provided in an inner space of the seat back frame, a support body supporting a part of the spring member to be able to move in front and back directions relative to the seat back by a drive device, and a retracting restriction mechanism disposed between the support body and the drive device or between the support body and the spring member to prevent the spring member from moving backward relative to the seat back when a load toward the spring member is equal to or more than a predetermined value.

BRIEF DESCRIPTION OF THE DRAWINGS

[0007] The foregoing and additional features and characteristics of the present invention will become more apparent from the following detained description considered with reference to the accompanying drawings in which like reference numerals designate like elements:

[0008]FIG. 1 is a perspective view of a seat frame including a lumbar support device according to a first embodiment of the invention;

[0009]FIG. 2 is a perspective view of the lumbar support device according to the first embodiment of the invention;

[0010]FIG. 3 is a cross sectional view taken along a line A-A shown in FIG. 2 showing a condition in which a support plate 52 is pulled backward completely;

[0011]FIG. 4 is a cross sectional view taken along a line A-A shown in FIG. 2 showing a position of a lumbar support being adjusted for a normal driving condition;

[0012]FIG. 5 is a cross sectional view taken along a line A-A shown in FIG. 2 showing a crankshaft 16 being pushed further than a condition shown in FIG. 4;

[0013]FIG. 8 is a view taken from an arrow B shown in FIG. 1 showing a position of a support plate 52 shown in FIG. 3;

[0014]FIG. 7 is a view taken from an arrow B shown in FIG. 1 showing a position of a support plate 52 shown in FIG. 5;

[0015]FIG. 8 is a perspective view of a seat frame including a lumbar support device according to a second embodiment of the invention;

[0016]FIG. 9 is a view taken from an arrow C shown in FIG. 8 showing a condition in which a lumbar support is pulled backward completely;

[0017]FIG. 10 is a view taken from an arrow C shown in FIG. 8 showing a condition in which a lumbar support is raised completely; and

[0018]FIG. 11 is a side view of a seat including a lumbar support device according to the invention.

DETAILED DESCRIPTION OF THE INVENTION

[0019] A first embodiment of a lumbar support device according to the present invention will now be described with reference to FIG. 1 through FIG. 7 and FIG. 11.

[0020] As shown in FIG. 11, a seat 1 is provided with a seat cushion 3, a seat back 2 operatively connected to the seat cushion 3 tiltable relative to the seat cushion 3 by a hinge mechanism 4, and a head rest 9 provided on an upper portion of the seat back 2.

[0021] As shown in FIG. 1, the seat back 2 is provided with a seat back frame 21 which is used as a reinforcement member and disposed inside of an outer cover 23 (FIG. 7) covering the seat back 2 and a cushion body 24 (FIG. 7). The seat back frame 21 is of substantially an inverted U-shape, and is comprised of a pair of side frames 25 disposed in a lateral direction relative to a seat back 2 and an upper frame 26 connected to upper ends of the respective side frames 25. A flat spring member 7 is provided in an inner space of the inverted U-shaped seat back frame 21. The flat spring member 7 is suspended by a plurality of suspension wires 75. One end of the suspension wires 75 is engaged with side frames 25 located at the lateral direction relative to the seat back 2, and the other end of the suspension wires 75 are engaged with frame portions 73 which correspond to an outer periphery of the flat spring member 7.

[0022] The frame portions 73 are located at both sides of the flat spring member 7, extending in a vertical direction relative to the seat back 2, and in a space within the frame portions 73, a plurality of linear springs 71 made of steel wires formed with flexing portions are tensioned in a horizontal direction relative to the seat back 2 in a central portion in the longitudinal direction of the linear spring 71, a string-shaped spacer 76 extending in the vertical direction relative to the seat back 2 is disposed in parallel with the frame portions 73. The spacer 76 is disposed to maintain each of the vertical spaces of the linear springs 71 equal to each other.

[0023] As shown in FIG. 1 and FIG. 11 a lumbar support device 10 is disposed inside of the seat back 2. Furthermore, as shown in FIG. 2 showing an enlarged view of the lumbar support device 10, the lumbar support device 10 has a crankshaft 16. The crankshaft 16 is extending in the lateral direction relative to the seat back 2, and is formed in a shape of a pipe with a bent portion to have a central portion 16 c relative to both ends 16 a and 16 b of the crankshaft 16. One end portion 16 a of the crankshaft 16 is rotatably supported by one of the side frames 25, and a sector gear 14 is fixed to the other end portion 16 b. In addition, the sector gear 14 is rotatably supported by a bracket 15 fixed to the other of the side frames 25 by a pin 13. A central axis of the pin 13 corresponds to a central axis of one end portion 16 a of the crankshaft 16 on the same line, and by a rotation of the sector gear 14, the central portion 16 c located at the center of the crankshaft 16 can move forward and backward in forward and backward directions relative to the seat back 2.

[0024] A drive device 41 is attached to the bracket 15 fixed to the other of the side frames 25. The drive device 41 has a pinion (not shown) engaging with the sector gear 14, and when a passenger operates a switch (not shown) for a power supply, the sector gear 14 is rotatable in either forward or backward direction relative to the seat back 2. As a result, the central portion 16 c located at the center of the crankshaft 16 can be moved forward and backward relative to the seat back 2 by rotating the crankshaft 16.

[0025] Next, as shown in FIG. 2 and FIG. 6, a leaf spring 51 is fixed to the central portion 16 c of the crankshaft 16 in the longitudinal direction of the crankshaft 16. Furthermore, a support plate 52 is disposed at a front side of the leaf spring 51 by inserting a positioning portion 51 a of the support plate 52 into a positioning hole 52 a disposed at the support plate 52. The support plate 52 is biased by the leaf spring 51 in a front direction of the seat back 2 relative to the crankshaft 16.

[0026] As shown in FIG. 6, a stopper 53 is disposed at a portion of the leaf spring 51 positioned in a back surface of the support plate 52. As shown in FIG. 7, when a load from the front side of the support plate 52 is applied, and becomes greater than a predetermined value, the stopper 53 is brought into contact with an upper portion of the leaf spring 51 which retains the crankshaft 16, preventing further bending of the leaf spring 51. Thus, by the stopper 53 and the leaf spring 51 being in contact with each other, a retracting restriction mechanism 50 prevents the support plate 52 and the flat spring member 7 supported by the support plate 52 relative to the seat back frame 21 from moving backward when the load greater than the predetermined value is applied.

[0027] On the other hand, projecting portions 54 are formed on both ends of the support plate 52 in a lateral direction relative to the seat back 2. As shown in FIG. 7, when the load greater than the predetermined value is applied to the support plate 52 from the front surface side thereof, the stopper 53 is brought into contact with the leaf spring 51, and at the same time, the projecting portions 54 are also brought into contact with the central portion 16 c of the crankshaft 16. By this structure, the support plate 52 as a whole is bent in accordance with a shape of the passenger's lumbar.

[0028] As shown in FIG. 1, the support plate 52 is disposed behind the frame portions 73 located at both sides of the flat spring member 7, extending in the vertical direction relative to the seat back 2. Therefore, when the drive device 41 is operated to push the support plate 52 in a front direction relative to the seat back 2, the frame portions 73 is also pushed forward. By this structure, the seat back 2 as a whole is moved forward, and the lumbar of the passenger is pushed on a smooth surface of the seat back 2.

[0029] An operation of the lumbar support device 10 according to the first embodiment of the invention will now be described,

[0030]FIG. 3 shows positions of the support plate 52 and the leaf spring 51 under a condition in which the support plate 52 is pulled backward completely so that the lumbar support is not applied. FIG. 4 shows conditions of the support plate 51 and the leaf spring 52 at the position of the lumber support being adjusted when the lumber support device 10 is used in a normal driving condition. Under the conditions shown in FIG. 3 and FIG. 4, the stopper 53 is not in contact with the leaf spring 51, having a space for bending. Under these conditions, the lumber support device 10 elastically supports a load from a passenger. From the condition shown in FIG. 4, when the crankshaft 16 is rotated further and the lumbar support is adjusted to a position shown in FIG. 5, a part of the seat back 2 corresponding to a lumbar of the passenger is pushed further to a forward direction. Then, the load applied to the support plate 52 from the frame portions 73 increases, and a load needed to support the passenger increases as well. As the load increases, the stopper 53 reaches the leaf spring 52. Consequently, the stopper 53 is brought into contact with the leaf spring 51. Since the leaf spring 52 which retains the support plate 52 is blocked by the stopper 53, the support plate 52 cannot move backward any more. By this structure, the seat back 2 can push the passenger's lumbar firmly. For instance, if the passenger reclines the seat back 2 nearly to a flat position to use a seat in a shape of a bed, a projecting portion of the seat back 2 can support the passenger without moving backward. Consequently, the passenger can use the lumbar support device 10 to stretch a body on the seat back 2 in order to reduce fatigue.

[0031] In this structure, by reducing the bending space of the leaf spring 51 or by increasing the spring rate of the leaf spring 51, the lumbar support device can be adjusted to move further to the forward direction or to make more difficult to move backward even when used in a normal sitting position so that the passenger can use the lumber support more effectively.

[0032] Next, a lumber support device 170 according to a second embodiment of the invention will be explained with reference to FIG. 8.

[0033] A lumber support device 110 is not provided with a support plate, and the frame portions 73 located in both sides of the flat spring member 7, and extending in the vertical direction relative to the seat back 2 is pushed directly by a projecting portion 116 c located at a center of a crankshaft 116 from a back of the flat spring member 7. In an actual design, an elastic member can be interposed between the projecting portion 116 c and the frame portions 73 to prevent an abrasion and abnormal noise. One end 116 a of the crankshaft 116 is rotatably supported by a bracket 118 welded to one of the side frame 25, and the other end 116 b is fixed to an arm 117 by welding (FIG. 9 and FIG. 10). The arm 117 is rotatably disposed by a hinge pin 113 at a bracket 115 fixed to the other of the side frames 25. A central axis of the hinge pin 113 and a rotation axis of the one end 116 a of the crankshaft 116 correspond to one another.

[0034] As shown in FIG. 9 and FIG. 10, a sector gear 114 is disposed rotatably at the hinge pin 113. Then, hooking portions 114 a and 114 b formed in portions of the sector gear 114 and a spring 151 engaged with the other end 116 b of the crankshaft 116 are also disposed at the hinge pin 113. The spring 151 provides a spring force to push the projecting portion 116 c of the center of the crankshaft 116 in a forward direction of the seat back 2 relative to the sector gear 114.

[0035] In this embodiment, a drive device 140 which manually operates a rotation of the sector gear 114 is disposed. In the drive device 140, a pinion 119 engaging with a gear 114 c formed on the sector gear 114 is rotatably disposed by a shaft 141 at a bracket 115. The shaft 141 is rotated by operating an operational lever 142 (FIG. 8) to rotate the sector gear 114. Furthermore, a position of the sector gear 114 after being rotated is maintained by a brake mechanism 141 a placed between the shaft 141 and the bracket 115.

[0036] An operation of the above described lumber support device 110 according to a second embodiment of the invention will now be described.

[0037]FIG. 9 shows a position of the sector gear 114 where the lumber support device 110 is not operated, in other words, a condition in which the sector gear 114 is rotated to the furthest back side of the seat back 2. Under this condition, the load applied to the part of the seat back 2 corresponding to the passenger's lumbar is supported by a spring force of the spring 151 at the projecting portion 116 c of the center of the crankshaft 116. When the load is applied to the seat back 2, the spring 151 can be bent from a position in which an edge portion of the arm 117 shown in FIG. 9 is brought into contact with a stopper 153 a disposed at a back portion of the sector gear 114 to a position in which the other end portion 116 c of the crankshaft 116 is brought into contact with a stopper 153 b disposed at a front portion of the sector gear 114. By this structure, the passenger is supported by a space between the other end portion 116 c and the stopper 153 b which absorbs a vibration and provides appropriate cushion characteristics during driving.

[0038] On the other hand, FIG. 10 corresponds to the condition shown in FIG. 5 of the first embodiment, showing a condition in which the seat back 2 is moved furthest to the forward direction. Under this condition, the sector gear 114 is rotated completely in a forward direction, and because of the position of the sector gear 114, the projecting portion 116 c of the center of the crankshaft 116 is pushing the frame portions 73 in the front direction of the seat back 2. Also, the other end portion 116 b of the crankshaft 116 is brought into contact with the stopper 153 b disposed at a front portion of the sector gear 114 by the spring force of the spring 151, rotating against the load applied to the seat back 2, to secure a projection of the seat back 2. Thus, a retracting restriction mechanism 150 which prevents the projecting portion 116 c and the flat spring member 7 supported by the projecting portion 116 c from moving backward when the load is equal to or greater than the predetermined value is formed by an interaction of the stopper 153 b, the spring 151, and the arm 117. In addition, the lumber support device 110 of the second embodiment can also be operated by having the same functions as the lumber support device 10 of the first embodiment.

[0039] According to the present invention, the lumber support device adjusts front and back movements of the seating surface of the seat back corresponding to the position of the passenger's lumber, and under the condition in which the lumber support is raised completely, the lumber support device can secure the projection of the lumber support even when the great load from the passenger's side is applied to the seat back. Therefore, the passenger can use the lumber support device when stretching a body to reduce fatigue.

[0040] By the above structure, with the seat back provided with the lumbar support device according to this invention, even when the load greater than the predetermined value is applied to the part which supports a lumbar of a passenger, a projection of the part which supports the passenger's lumbar is maintained by the retracting restriction mechanism. 

What is claimed is:
 1. A lumbar support device for a vehicle seat comprising; a seat back frame comprising a pair of side frames located right and left sides of a seat back and extending in a vertical direction relative to the seat back and an upper frame connecting an upper portion of each side frame; a spring member provided in an inner space of the seat back frame; a support body supporting a part of the spring member so as to be movable in front and back directions relative to the seat back by a drive device; and a retracting restriction mechanism disposed between the support body and the drive device or between the support body and the spring member to prevent the spring member from moving backward of the seat back when a load applied to the spring member is equal to or more than a predetermined value.
 2. A lumbar support device as recited in claim 1, wherein the retracting restriction mechanism includes a leaf spring which is fixed to the support body, a support plate which is connected to the support body through the leaf spring and which moves the spring member and a stopper which is disposed between the leaf spring and the support plate and which is able to contact with the leaf spring and the support plate when the load applied to the spring member is equal to or more than the predetermined value.
 3. A lumber support device as recited in claim 2, wherein the support plate includes a projection which is projected toward the support body and which is contacted with the support body when the load applied to the spring member is equal to or more than the predetermined value.
 4. A lumbar support device as recited in claim 1, wherein the retracting restriction mechanism includes an arm which is fixed to the support body, a support spring which is disposed between the support body and the drive device so as to urge the support body in the front direction of the seat back relative to the drive device and a stopper which is disposed between the arm and the drive device and which is able to contact with the arm and the drive device when the load applied to the spring member is equal to or more than the predetermined value. 